The present invention relates to lightning protection for wind turbines. More particularly, the invention relates to lightning protection for wind turbines and lightning protecting for rotor blades of wind turbines. Specifically, the invention relates to a rotor blade, a lightning protection system, and a method of manufacturing a rotor blade.
Damage to wind turbines due to lightning strikes has been recognized as an increasing problem. The influence of lightning faults on the reliability of wind turbines and wind farms may become a concern as the capacity of wind turbines increases. This is particularly the case when several large wind turbines are operated together in wind farm installations because the potential loss of multiple large production units due to one lightning strike may be significant. Unlike other electrical installations such as overhead lines and power plants, it is more difficult for wind turbines to provide protective conductors that can be arranged around or above the wind turbine. This is due to the physical size and nature of wind turbines. Wind turbines typically have two or three blades with a diameter of several tens of meters up to 100 m or more. The rotor rotates high above the ground. In addition, there is extensive use of insulating composite materials, such as glass fiber reinforced plastic, as load-carrying parts. Aerodynamic considerations and consideration of the fast rotating blades also have to be taken into account for a lightning protection system.
The lightning conduction system of a typical wind turbine blade consists of one or more metallic receptor(s) connected to a down conductor that carries the strike from the receptor(s) to the blade bearing and eventually through the tower to the ground. Lightning is striking the blades and is primarily not noticeable unless there is external damage. However the internal connections of the down conductor may be damaged and are not easily found unless they are checked for continuity by comparing the ohm response between the receptor(s) and the tower or ground. To access the blade tip receptor it requires a crane or expensive man basket apparatus. This testing process is labor intensive, difficult and costly, and can only be performed as the weather permits.